[Misiur]

pawn Код:

static
    PlayerExtinguisherAmmo[MAX_PLAYERS],
    PlayerExtinguisherTimer[MAX_PLAYERS]
;
//...
forward ExtinguisherAmmoTimer(playerid);
public ExtinguisherAmmoTimer(playerid)
{
    if (--PlayerExtinguisherAmmo <= 0) {
        KillTimer(PlayerExtinguisherTimer);
        //eventually change weapon to something else so he can't use extinguisher anymore
    }
    return 1;
}

Now, OnPlayerKeyStateChange when fire button is pressed start this timer on repeat, and on button release kill it as well. Recharge the ammo when you deem it should be recharged.