Games like Mash Box
Games like Mash Box include skate., BMX Streets, Garry's Mod, VRChat, and Goat Simulator. We matched them by the tags players give Mash Box on Steam (Casual, Simulation, Sports, Sandbox, and 3D): closest matches first, and among equally close ones the better-known games.

skate.
Shared: Multiplayer · Sports · Sandbox

BMX Streets
Shared: Simulation · Sports · Sandbox

Garry's Mod
Shared: Sandbox · Casual · Multiplayer

VRChat
Shared: Multiplayer · Free to Play · Simulation

Goat Simulator
Shared: Simulation · Sandbox · Casual

PowerWash Simulator
Shared: Casual · Simulation · 3D

ScootX
Shared: Casual · Sports · Simulation

CarX Drift Racing Online
Shared: Simulation · Sandbox · Multiplayer

ScooterFlow
Shared: Simulation · Sports · Multiplayer

Golf With Your Friends
Shared: Casual · Sports · Multiplayer

House Flipper
Shared: Simulation · Casual · Multiplayer

Session: Skate Sim
Shared: Simulation · Sports · Skateboarding

SuchArt: Creative Space
Shared: Simulation · Sandbox · Free to Play

Wobbly Life
Shared: Simulation · Sandbox · Multiplayer

Skater XL - The Ultimate Skateboarding Game
Shared: Sports · Sandbox · Multiplayer

Golf It!
Shared: Casual · Sports · Multiplayer

Fishing Planet
Shared: Simulation · Sports · Multiplayer

BeamNG.drive
Shared: Simulation · Sandbox · Multiplayer

Disney Speedstorm
Shared: Multiplayer · Casual · 3D

SMITE®
Shared: Multiplayer · Third Person · Free to Play

Undisputed
Shared: 3D · Third Person · Sports

Marvel Rivals
Shared: Multiplayer · Free to Play · Casual

Into The Flames
Shared: Simulation · Casual · Sandbox

Ultimate Fishing Simulator
Shared: Simulation · Sports · 3D