Anyone know what’s wrong with my car?

Make: Daihatsu Model: Mira Gino Year: 2006 Mileage: 111,000 km

Quick background. Went traveling for 2.5 months for work and i left my car outside. i live near the coast. the car was filled with gas when i left and when i returned the car drove just fine.

i was home for 1 week and then i went on vacation for the holidays. i was gone roughly 18 days but this time i had stored my car inside my garage.

when i came home my car immediately felt off. This is what i’ve gathered:

• No engine lights showing on dash
• loss of power when i hit the gas pedal (barely makes it up hills)
• Very Rough idle (feels like it’s gonna stall at any moment)
• Exhaust is sputtering (almost sounds like a go-kart)

My thoughts- Bad gas or Bad spark plugs?

Any advice or help would be greatly appreciated. Thanks.