I hardly doubt there's a good strategy for toin coss, with a chance of 50/50 that pretty much resets for every round, you can only use techniques to actually limit your losses. Most, if not all results of a toin coss are pretty much just based on luck, so if you can keep a straight head, you won't really suffer that much by playing with it for long.
I dont know why you do called martingale isnt a strategy yet its considered one of the most common ways on where people do make use of this technique.It might be common but it do somehow actually works or not
depending on the person been using it.Its just a simple add % of bet on every loss but we know that losing streak can really fuck us up.
The difference on a toss coin is that its impossible for you not to have head or tails on several bets not like when you do play dice online where chances of streak is high.
I havent tried on playing toss coin online but i do remember that theres some website whom do offer this game.
Techniques? Theres no such thing that guaranteed profits or winning but you can at least make out some control or limits which make yourself to be on the green side.
It isn't a strategy mostly due to how the terms are used most likely, it's more suitable to describe it as a technique, instead of a strategy. Though I do agree that it could be considered one, ignoring the definite definitions since the two are mostly used interchangeably after all.
Indeed, there's no guaranteed way to actually profit off of anything, and techniques and strategies are only ways for you to actually avoid being in the read. A good example would be as you said, martingale, which provides you with at least the minimal profit as long as you have enough funds to support it.