Bbq Spare Ribs Marinated in Celtic Salt with a Maple Syrup Sauce

1.5 kg of spare ribs

Marinade:

250 ml of apple cider vinegar
1 L of water
2 tablespoons of freshly ground black pepper
1 tablespoon of Jamaican chillies
1 tablespoon of juniper berries
4 crushed garlic cloves
1 bouquet garni of thyme and rosemary
2 tablespoons of Celtic Coarse salt

BBQ maple syrup sauce:

200 ml of ketchup
1 tablespoon of ginger
3 tablespoons of apple cider vinegar
250 ml of maple syrup
2 teaspoons of mustard seeds
2 garlic cloves
200 ml of water 

For baking:

1 bottle of lager
1 onion
2 green chillies