San Jose tied it 2-2 at 4:17 of the third period when Hertl scored his first goal from in front on a rush.
"I'm happy to score two goals, but we can't be real happy about the last two games," Hertl said. "They weren't our best games. We have to get some rest and play a little bit better against these teams who are a little bit lower than us. We have to put teams away earlier in games and not keep hunting points."
Garland put the Coyotes ahead 3-2 when he scored his second NHL goal at 6:06 on a breakaway. He scored his first goal in a 6-4 win against the Colorado Avalanche on Saturday.
"I didn't want to wait too long for the next one," Garland said. "I waited awhile for the first. It was nice. Obviously, in a huge game like that, it was nice to get it."
Hertl scored his second of the night at 13:53 on a wraparound to tie it 3-3.
The Sharks had a power play in overtime, when they outshot the Coyotes 8-1.
"They're a great team," said Kuemper, who ended his six-game losing streak. "They had a big push in their own building. They tied it up, but we were able to kind of hit the brakes after that happened and keep ourselves in it, and then get a big shootout win."