We remodeled our bathroom. Part of the remodel was installing 2 new bathroom sinks and faucets.

Tonight my husband finished by installing the final faucet. That is the only thing he did. After installing it, when we turned on any hot water in the entire house, it comes out for a few seconds then trickles to barely a stream. The hot water heater sounds like it is filling for just those few seconds and then it stops.

Before he did this we had no problems at all with our hot water heater or pressure. We have a 1 year old electric hot water heater. We live in an 8 year old 28 x 60 mobile home. Help!

You have a drain valve at the bottom of the water heater, connect a water hose on it and open the valve and see how fast the water runs out of the hose. Also listen and se if you hear the noise like the water heater filling.
If you have lots of water coming out of the hose that will tell you that it is not the inlet of the water heater. From there you need to check the water coming out on the hot side. Do you have any knid of turn off valve on the hot water side of the heater.
I think the noise you hear is the water that comes out of the faucets with a force is the water that is pressurized in the lines, but as the pressure drops and you turn off the faucet the noise is the water coming out of the heater and building pressure in the hot water pipe again.

I have an idea the inlet side of your water heater is restricted and that is why you hear the noise at the heater. Let me know if this helps you.

Although there could be crud in the lines, did you drain the hot water heater?

If so, you must let the air flow out to a faucet. If you left the power on to an empty tank, you may have burned the elements out. If once you have water flowing out the tank and it doesn't heat, you will have to replace the elements.