Johnny Manziel -- Aerobics Instructor ... In New Snickers Commercial!!!

Move over Jane Fonda ... 'cause Johnny Manziel is an aerobics instructor now.

Kinda.

The Cleveland Browns quarterback is the star of a new Snickers commercial where he plays a leggings-wearing, headband-sporting exercise teacher ... leading a class full of confused women.

It's all a part of those "You're Not You When You're Hungry" ads ... complete with the epiphany that he's supposed to be on a football field instead of an aerobics studio.

So, if you're keeping score -- that's TWO endorsement deals for the backup QB in Cleveland.