Super Mario Boards

Mario because he can manipulate parallel universes by jumping backwards.

*Cuts to a Smash-style victory screen where the hot dog vender is now filthy stinking rich in coins and rings*

I imagine that Sonic would be honoured to be able to meet his idol, because if we put a real-world parallel to the games, Sonic is inspired to start his own series because he idolises Mario and got off and do something on his own. Mario being the friendly chap he is, would be happy to meet Sonic. That's why they are in good terms in the Olympics.

So basically it's in line with what you mentioned.

Thank you for reading.

I mean we already know how they interact from Olympics, they're good friends.

My follow up to this question is "where?", because it really comes down to what physics are in place. In the Olympics universe everyone's powered down to practically irl human ability, in Smash everyone's either powered up or down in accordance to give them a mutual fighting chance against each other.
Following that logic, if we were to have a match between a Mario from a canon platformer against a Sonic from a respective canon platformer, it'd still come down to who's playing them, as their canon platforming universes dictate the idea that they can get through any obstacle as long as they have the right momentum, timing, and choices of their actions, while 1 mistake could cost them a life, like running into a goomba or off a cliff.
eg. They both have OP Nimble Attacks, but they both also have weak point openings with all of their moves. Mario could swing his cape and get conked on the head, or Sonic could use his homing dash and get deflected and then get hit on his recovery, or even get hit by a fireball or koopa shell while he's homing in

It also depends on which Mario and Sonic we're talking about seeing as they both have many different interpretations with differing boons and banes across the various spin-offs and external media such as the cartoons, movies, anime, comics and manga.

@Starfire neat so Mario can buy multiple hotdogs with just the same money and still follow the law.

@Crow yeah we all know the real winner lol.

In the main games, every time a level ends Mario's coin count reduces to zero, impacting Mario's ability to afford a hot dog. Hot dogs make Mario grow twice his size, curing him of stature problems, but more hot dogs would just convert to points, unless it's Super Mario Bros. 2 incarnation. In Mario Party though, coins are easy to get and not really hard to lose without getting chomped by a Piranha Plant or Bowser persuading to mugging you. But in the RPGs, Mario can have all the coins he likes and carry an infinite amount of hot dogs, so that's Mario's strongest incarnation.

Sonic can stockpile on rings better than Mario so he can buy hot hodgs for Mario, but he can lose all rings when getting hit so he has to be careful, and rings reset if he completes a level, though he does get graded, which can motivate him to collect more rings. Especially if he's at a hot dog stand. Sonic has items that let him vacuum rings for instance rather than onerously collect them like Mario does. Sonic does travel super fast but he's no pickpocketer, but I suppose he can do much more work in less time.

@Wallop Hm yeah I can imagine they can try to wow the hot dog vendor with their nimble moves, maybe try juggling the ingredients or running like crazy to increase air friction to cook the meat. One mistake is costly though. I don't think running off a cliff will improve hot dog flavors, and Goombas, of course, cannot resist the delectable and lovable gristle mish mash. Mario could swing his cape but that just makes the hot dog cold and causes birds to fly and grab the meat, hitting Mario in the head. Sonic's homing dash can miss a hot dog and he'll just bounce off and get hit by Mario's fireball, which also missed the hot dog. All these flaws will help ensure the match is fair, however.

Just take Sonic's speedy shoes off. We'll see how well can he deal against our plumber boy bare handed.