Motorcycle electrics?

I bought generic heated grips for my Honda CBF 125. Problem is that the wire doesn't reach the battery. The Ebayer said they run off the speed controller whatever that is. Can anyone help with this? I'm a complete noob.

Go back to the store where you bought the grips and tell them you need a wire stretcher. They'll be happy to help.

If wired up direct to the battery and you accidently leave them switched on they will kill the battery while you are away from the bike. I know people who have done just that.
Your bike does not have a "Speed Controller" other than you as the rider!
One wire usually goes to the earth which can be the battery negative
The other wire needs to go to a switched positive supply that goes off when you turn off the ignition switch. It also needs to be fused appropriately.

I think you need some hands on help from someone who really knows what to do. Everyone has to learn like this sometime.

Speed controller? Makes no sense. Maybe inside the speedometer housing there's a voltage source, or inside the headlight housing. Or just extend the wires to the battery.

You need a SWITCH (like an ON/OFF). Direct to the battery is not an option.

It is common to use a PWM control to control the power going to grips/gloves/heated clothing. They are also used (were designed for) speed control in DC motors.
Something to read?

A couple of but splices and some wire will make it to the battery.
A simple on/off switch will work, but you may have to turn it on and off to keep from getting too warm. A fuse is recommended.

Here's the bad news: the charging systems on most teensy tiny bikes like yours put out maybe 200 Watts on a good day. The bike needs close to 200 Watts to run the lights, ignition system, and recharge the battery after it starts the engine. Hope it works, but I would check the bike's alternator output specs and the info about the power consumption of the grips before installing them. You can also do a temporary hookup, start the bike, then turn em on and see if the bike can maintain its regular charging voltage of around 14 volts. I would look into rechargeable battery powered heated gloves instead. Wish you'd asked me first, dude.

I doubt that the alternator on a CBF125 has enough output to drive heated handgrips.